1. Field of the Invention
The invention relates to, for example, a technical field of a vehicle control apparatus controlling a vehicle capable of performing regenerative electric power generation.
2. Description of Related Art
A vehicle capable of performing regenerative electric power generation, such as a hybrid vehicle and an electric car, is known. The vehicle is provided with a rotary electric machine (for example, a motor generator or an alternator) having, for example, a rotating shaft directly or indirectly connected to a drive shaft of the vehicle so as to perform the regenerative electric power generation. In this case, the kinetic energy of the vehicle is converted into the rotational energy of the rotating shaft of the rotary electric machine, and thus the rotary electric machine can apply a regenerative braking force offsetting the kinetic energy of the vehicle to the vehicle while generating electric power.
Japanese Patent Application Publication No. 2011-056969 (JP 2011-056969 A) and Japanese Patent Application Publication No. 2011-097666 (JP 2011-097666 A) disclose examples of the vehicle performing the regenerative electric power generation. JP 2011-056969 A, in particular, discloses a vehicle in which the regenerative braking force decreases (that is, the electric power that is generated by the regenerative electric power generation decreases) as the speed of the vehicle decreases and the regenerative braking force becomes zero (that is, the regenerative electric power generation stops) when the speed of the vehicle decreases to a certain predetermined value.
The electric power that the rotary electric machine generates by the regenerative electric power generation is input into a battery (or any electric power storage device such as a capacitor). As a result, the battery is charged with the electric power that the rotary electric machine generates by the regenerative electric power generation. Accordingly, a method for increasing the amount of the electric power that the rotary electric machine generates by the regenerative electric power generation is one of the methods for increasing the amount of the charging of the battery (that is, the amount of the electric power that is input into the battery).
It is considered to be preferable to decrease the vehicle speed at which the regenerative electric power generation stops to the minimum (typically, to zero) so that the amount of the electric power that the rotary electric machine generates by the regenerative electric power generation increases. In a case where the vehicle speed is relatively or extremely low, however, the electric power that is generated by the rotary electric machine may not be input into the battery (that is, the battery may not be charged). Alternatively, in a case where the vehicle speed is relatively or extremely low, the electric power may be output from the battery (that is, the battery may be discharged) despite the generation of the electric power by the regenerative electric power generation performed by the rotary electric machine.
For example, it is practically rare that the entire electric power that the rotary electric machine generates by the regenerative electric power generation is input into the battery. Specifically, at least part of the electric power that the rotary electric machine generates by the regenerative electric power generation may become a loss attributable to the rotary electric machine itself. In addition, at least part of the electric power that the rotary electric machine generates by the regenerative electric power generation may become a loss attributable to various types of electric power equipment in view of the fact that the various types of electric power equipment (for example, inverter, converter, and the like) arranged between the rotary electric machine and the battery need to be driven for the rotary electric machine to perform the regenerative electric power generation. In a case where the vehicle speed is relatively or extremely low, the amount of the electric power that the rotary electric machine generates by the regenerative electric power generation is relatively or extremely small as well. Accordingly, if the rotary electric machine performs the regenerative electric power generation even in a case where the vehicle speed is relatively or extremely low, the entire electric power that the rotary electric machine generates by the regenerative electric power generation may be consumed as a loss or the electric power may be output from the battery to drive the various types of electric power equipment. It cannot be said that these situations are preferable because these situations exacerbate the efficiency of the use of the battery.
If the vehicle speed at which the regenerative electric power generation stops becomes relatively higher, a situation becomes less likely to occur in which the electric power is output from the battery despite the generation of the electric power by the regenerative electric power generation of the rotary electric machine. In a case where the regenerative electric power generation is stopped in a state where the vehicle speed is relatively high, however, the regenerative electric power generation may be stopped despite the amount of the electric power that the rotary electric machine generates by the regenerative electric power generation being correspondingly large. As a result, the amount of the electric power that is input into the battery from the rotary electric machine during the regenerative electric power generation may be excessively decreased (that is, decreased more than necessary).
In the related art for adjusting the regenerative braking force (or stopping the regenerative electric power generation) based on the vehicle speed, it is technically difficult, as described above, to correspondingly or relatively increase the amount of the electric power that is input into the battery from the rotary electric machine during the regenerative electric power generation while suppressing the output of the electric power from the battery during the regenerative electric power generation. In other words, in the related art for adjusting the regenerative braking force (or stopping the regenerative electric power generation) based on the vehicle speed, it is technically difficult to suppress both the output of the electric power from the battery during the regenerative electric power generation and an excessive decrease in the amount of the electric power input into the battery from the rotary electric machine during the regenerative electric power generation.